1. Field of the Invention
The present invention relates to a method and apparatus for managing power of a portable information device.
2. Description of the Related Art
Mobile terminals allow users to perform operations while they are moving. However, when a user carries a mobile terminal, in his/her pockets or bag, a power button or a hardware button installed on the mobile terminal can be accidentally pressed or a touch screen can be unintentionally touched, thereby turning on the mobile terminal. Also, the mobile terminal may be turned on by an alarm signal or a received phone call.
FIG. 1 is a flowchart showing a power state of a conventional portable information device according to the prior art. Referring to FIG. 1, when a user turns the power 120 on, the portable information device is changed to a normal operating state 130 from a no-power state 110. In the normal operating state 130, the user can use the portable information device to conduct communications or data processing.
When a battery voltage of the portable information device decreases below a predetermined threshold voltage while the device is being used, the portable information device enters a suspend state 140 in which the clock speed of a CPU (central processing unit) is reduced and only predetermined operations are performed such that power can be saved.
If the battery is not charged during this suspend state 140, the voltage level drops gradually and the portable information device goes back to the no-power state 110.
Meanwhile, in the suspend state 140, the portable information device may be unintentionally turned on by accidentally pressing the power button on the terminal. In such case, since the portable information device cannot identify whether the button is pressed intentionally or unintentionally, the terminal advances to the normal operating state 130 again and consumes an amount of power for a long time, resulting in the battery of the portable information device to be further exhausted.
FIG. 2 is a schematic configuration diagram of a power management device of the portable information device according to the prior art. Referring to FIG. 2, the power management device includes a CPLD (Complex Programmable Logic Device) 210 sending an interrupt signal to a CPU (Central Processing Unit) 220 by detecting battery voltage and a CPU 120 (FIG. 1) setting the portable information device to enter a suspend mode based on the interrupt signal sent by the CPLD 210. The CPLD 210 is connected to a voltage detecting unit 212 to detect if the voltage of a battery 211 falls below a predetermined threshold voltage. The CPLD 210 is connected to a GPIO (general purpose input-output) unit of the CPU so that the CPU 120 can detect a power failure when the voltage of the battery 211 falls below the predetermined threshold voltage and can enter a sleep mode (a suspend state).
When the CPU 220 receives the interrupt signal indicating that the battery voltage falls below the predetermined threshold voltage from the CPLD 210 through the GPIO, the CPU 220 sets the portable information device in the sleep mode, which is a low-power consumption state. For example, in the sleep mode, the clock speed of a CPU slows down and an I/O (input/output) device 240 including an LCD (liquid crystal display) and the like is changed from an active state to an inactive state.
As described above, the portable information device is switched from the sleep mode, which is a low-power state, to a normal operating state, in which a significant amount of power is consumed, when the portable information device is unintentionally activated, and therefore the battery voltage is needlessly consumed.